1. Field
Embodiments described below relate to a nonvolatile semiconductor memory device and a control method thereof.
2. Description of the Related Art
A NAND type flash memory is known as a nonvolatile semiconductor memory device which is electrically rewritable and capable of being highly integrated. A memory cell of the NAND type flash memory includes a charge accumulation layer formed on a semiconductor substrate via a tunnel insulating film and a control gate stacked on the charge accumulation layer via an inter-gate insulating film. The memory cell stores data in a nonvolatile manner by a charge accumulation state of the charge accumulation layer.
In this NAND type flash memory, the memory cell deteriorates as the number of times of write operations and erase operations increases. As a result, there is a risk that it becomes impossible to write data accurately in the write operation of data.